1. Field of the Invention
The present invention relates to an original feeding apparatus (ADF: automatic document feeder) which is used in an image forming apparatus such as a copying machine to feed an original to a predetermined position, or to an image forming apparatus having such an original feeding apparatus.
2. Description of the Prior Art
An ADF is used in an image forming apparatus such as a copying machine to sequentially feed documents or originals to the exposure position. In a conventional image forming apparatus of this type, when an interrupt copy operation is to be performed during a copy operation of a plurality of originals using the ADF, the interrupt key at a control panel of the copying machine must be depressed to stop the overall system. Thereafter, the ADF is opened to set the original to be copied in the interrupt copy operation. Thereafter the ADF is closed, and the copy start button is depressed. In order to resume the previous copy operation after the interrupt copy operation is performed, the remaining originals to be copied must be set in the ADF and the copy start button must be depressed again.
In this manner, the conventional ADF operates poorly and is cumbersome to the operator. In view of this, the user does not generally want to perform an interrupt copy operation but rather waits for a long copy operation to finish first.
In an ADF of this type, when the original is exposed, the ADF exchanges the originals to improve the copying speed.
When an abnormal conveyance such as jamming is detected in the copying machine, it is generally associated with the copy sheet which has already been discharged out of the copying machine. In such a case, in the conventional ADF, the operator must compare the copied sheets and the originals to check for the number of originals which have already been discharged outside the copying machine and must therefore be copied again. Then, the operator resets both originals (to be referred to as return originals hereinafter) which must be copied again, and originals remaining in the original tray, and then depresses the copy start key and the like to resume the copy operation.
In a conventional apparatus of this type, therefore, the operability against an abnormality such as jamming is poor. If the operator does not reset the return originals and the originals in the original tray but simply places the return originals on the originals in the original tray and depresses the copy start button, jamming is frequently caused and the originals may be damaged.
When jamming or the like occurs in the copying machine on which such an ADF is mounted, the next original which was being fed by the ADF may be at the exposure position. When the operator resumes the copy operation by depressing the copy start button after the abnormality is removed, the operator may forget to return this original and therefore fail to produce a copy of this original. Even if the operator remembers about this original, he must pick up the original to be copied again and perform the copy operation for this again, thus resulting in a cumbersome operation.
In an ADF of this type, during the copy operation of an original (to be referred to as a previous original) placed on a glass platen of the copying machine, an original (to be referred to as a next original) is conveyed to a position near the glass platen. As a result, the separation/convey operation of the next original may coincide with the exposure operation of the previous original. This results in an increase in power consumption of the overall system. Especially with a domestic copying machine wherein the total power consumption is limited to a predetermined value due to the power source capacity, a strict design requirement is imposed. This may prevent use of the system by a general user.